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Created March 26, 2017 18:08
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main.c
#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include "bitwit.h"
#include "usiTwiSlave.h"
void send_something(void)
{
usiTwiTransmitByte(0x11);
}
int main(int argc, char const* argv[])
{
usiTwiSlaveInit(0x15);
_onTwiDataRequest = send_something;
sei();
while (1) {
}
return 0;
}
Raw
usiTwiSlave.c
/********************************************************************************
USI TWI Slave driver.
Created by Donald R. Blake. donblake at worldnet.att.net
Adapted by Jochen Toppe, jochen.toppe at jtoee.com
---------------------------------------------------------------------------------
Created from Atmel source files for Application Note AVR312: Using the USI Module
as an I2C slave.
This program is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.
---------------------------------------------------------------------------------
Change Activity:
Date Description
------ -------------
16 Mar 2007 Created.
27 Mar 2007 Added support for ATtiny261, 461 and 861.
26 Apr 2007 Fixed ACK of slave address on a read.
04 Jul 2007 Fixed USISIF in ATtiny45 def
12 Dev 2009 Added callback functions for data requests
********************************************************************************/
#ifndef TEST
/********************************************************************************
includes
********************************************************************************/
#include <avr/io.h>
#include <avr/interrupt.h>
#include "usiTwiSlave.h"
//#include "../common/util.h"
/********************************************************************************
device dependent defines
********************************************************************************/
#if defined( __AVR_ATtiny2313__ ) | \
defined( __AVR_ATtiny2313A__ )
# define DDR_USI DDRB
# define PORT_USI PORTB
# define PIN_USI PINB
# define PORT_USI_SDA PB5
# define PORT_USI_SCL PB7
# define PIN_USI_SDA PINB5
# define PIN_USI_SCL PINB7
# define USI_START_COND_INT USISIF
# define USI_START_VECTOR USI_START_vect
# define USI_OVERFLOW_VECTOR USI_OVERFLOW_vect
#endif
#if defined( __AVR_ATtiny25__ ) | \
defined( __AVR_ATtiny45__ ) | \
defined( __AVR_ATtiny85__ )
# define DDR_USI DDRB
# define PORT_USI PORTB
# define PIN_USI PINB
# define PORT_USI_SDA PB0
# define PORT_USI_SCL PB2
# define PIN_USI_SDA PINB0
# define PIN_USI_SCL PINB2
# define USI_START_COND_INT USISIF
# define USI_START_VECTOR USI_START_vect
# define USI_OVERFLOW_VECTOR USI_OVF_vect
#endif
#if defined( __AVR_ATtiny26__ )
# define DDR_USI DDRB
# define PORT_USI PORTB
# define PIN_USI PINB
# define PORT_USI_SDA PB0
# define PORT_USI_SCL PB2
# define PIN_USI_SDA PINB0
# define PIN_USI_SCL PINB2
# define USI_START_COND_INT USISIF
# define USI_START_VECTOR USI_STRT_vect
# define USI_OVERFLOW_VECTOR USI_OVF_vect
#endif
#if defined( __AVR_ATtiny261__ ) | \
defined( __AVR_ATtiny461__ ) | \
defined( __AVR_ATtiny861__ )
# define DDR_USI DDRB
# define PORT_USI PORTB
# define PIN_USI PINB
# define PORT_USI_SDA PB0
# define PORT_USI_SCL PB2
# define PIN_USI_SDA PINB0
# define PIN_USI_SCL PINB2
# define USI_START_COND_INT USISIF
# define USI_START_VECTOR USI_START_vect
# define USI_OVERFLOW_VECTOR USI_OVF_vect
#endif
#if defined( __AVR_ATmega165__ ) | \
defined( __AVR_ATmega325__ ) | \
defined( __AVR_ATmega3250__ ) | \
defined( __AVR_ATmega645__ ) | \
defined( __AVR_ATmega6450__ ) | \
defined( __AVR_ATmega329__ ) | \
defined( __AVR_ATmega3290__ )
# define DDR_USI DDRE
# define PORT_USI PORTE
# define PIN_USI PINE
# define PORT_USI_SDA PE5
# define PORT_USI_SCL PE4
# define PIN_USI_SDA PINE5
# define PIN_USI_SCL PINE4
# define USI_START_COND_INT USISIF
# define USI_START_VECTOR USI_START_vect
# define USI_OVERFLOW_VECTOR USI_OVERFLOW_vect
#endif
#if defined( __AVR_ATmega169__ )
# define DDR_USI DDRE
# define PORT_USI PORTE
# define PIN_USI PINE
# define PORT_USI_SDA PE5
# define PORT_USI_SCL PE4
# define PIN_USI_SDA PINE5
# define PIN_USI_SCL PINE4
# define USI_START_COND_INT USISIF
# define USI_START_VECTOR USI_START_vect
# define USI_OVERFLOW_VECTOR USI_OVERFLOW_vect
#endif
/********************************************************************************
functions implemented as macros
********************************************************************************/
#define SET_USI_TO_SEND_ACK( ) \
{ \
/* prepare ACK */ \
USIDR = 0; \
/* set SDA as output */ \
DDR_USI |= ( 1 << PORT_USI_SDA ); \
/* clear all interrupt flags, except Start Cond */ \
USISR = \
( 0 << USI_START_COND_INT ) | \
( 1 << USIOIF ) | ( 1 << USIPF ) | \
( 1 << USIDC )| \
/* set USI counter to shift 1 bit */ \
( 0x0E << USICNT0 ); \
}
#define SET_USI_TO_READ_ACK( ) \
{ \
/* set SDA as input */ \
DDR_USI &= ~( 1 << PORT_USI_SDA ); \
/* prepare ACK */ \
USIDR = 0; \
/* clear all interrupt flags, except Start Cond */ \
USISR = \
( 0 << USI_START_COND_INT ) | \
( 1 << USIOIF ) | \
( 1 << USIPF ) | \
( 1 << USIDC ) | \
/* set USI counter to shift 1 bit */ \
( 0x0E << USICNT0 ); \
}
#define SET_USI_TO_TWI_START_CONDITION_MODE( ) \
{ \
USICR = \
/* enable Start Condition Interrupt, disable Overflow Interrupt */ \
( 1 << USISIE ) | ( 0 << USIOIE ) | \
/* set USI in Two-wire mode, no USI Counter overflow hold */ \
( 1 << USIWM1 ) | ( 0 << USIWM0 ) | \
/* Shift Register Clock Source = External, positive edge */ \
/* 4-Bit Counter Source = external, both edges */ \
( 1 << USICS1 ) | ( 0 << USICS0 ) | ( 0 << USICLK ) | \
/* no toggle clock-port pin */ \
( 0 << USITC ); \
USISR = \
/* clear all interrupt flags, except Start Cond */ \
( 0 << USI_START_COND_INT ) | ( 1 << USIOIF ) | ( 1 << USIPF ) | \
( 1 << USIDC ) | ( 0x0 << USICNT0 ); \
}
#define SET_USI_TO_SEND_DATA( ) \
{ \
/* set SDA as output */ \
DDR_USI |= ( 1 << PORT_USI_SDA ); \
/* clear all interrupt flags, except Start Cond */ \
USISR = \
( 0 << USI_START_COND_INT ) | ( 1 << USIOIF ) | ( 1 << USIPF ) | \
( 1 << USIDC) | \
/* set USI to shift out 8 bits */ \
( 0x0 << USICNT0 ); \
}
#define SET_USI_TO_READ_DATA( ) \
{ \
/* set SDA as input */ \
DDR_USI &= ~( 1 << PORT_USI_SDA ); \
/* clear all interrupt flags, except Start Cond */ \
USISR = \
( 0 << USI_START_COND_INT ) | ( 1 << USIOIF ) | \
( 1 << USIPF ) | ( 1 << USIDC ) | \
/* set USI to shift out 8 bits */ \
( 0x0 << USICNT0 ); \
}
/********************************************************************************
typedef's
********************************************************************************/
typedef enum
{
USI_SLAVE_CHECK_ADDRESS = 0x00,
USI_SLAVE_SEND_DATA = 0x01,
USI_SLAVE_REQUEST_REPLY_FROM_SEND_DATA = 0x02,
USI_SLAVE_CHECK_REPLY_FROM_SEND_DATA = 0x03,
USI_SLAVE_REQUEST_DATA = 0x04,
USI_SLAVE_GET_DATA_AND_SEND_ACK = 0x05
} overflowState_t;
/********************************************************************************
local variables
********************************************************************************/
static uint8_t slaveAddress;
static volatile overflowState_t overflowState;
static uint8_t rxBuf[ TWI_RX_BUFFER_SIZE ];
static volatile uint8_t rxHead;
static volatile uint8_t rxTail;
static uint8_t txBuf[ TWI_TX_BUFFER_SIZE ];
static volatile uint8_t txHead;
static volatile uint8_t txTail;
// data requested callback
void (*_onTwiDataRequest)(void);
/********************************************************************************
local functions
********************************************************************************/
// flushes the TWI buffers
static
void
flushTwiBuffers(
void
)
{
rxTail = 0;
rxHead = 0;
txTail = 0;
txHead = 0;
} // end flushTwiBuffers
/********************************************************************************
public functions
********************************************************************************/
// initialise USI for TWI slave mode
void
usiTwiSlaveInit(
uint8_t ownAddress
)
{
flushTwiBuffers( );
slaveAddress = ownAddress;
// In Two Wire mode (USIWM1, USIWM0 = 1X), the slave USI will pull SCL
// low when a start condition is detected or a counter overflow (only
// for USIWM1, USIWM0 = 11). This inserts a wait state. SCL is released
// by the ISRs (USI_START_vect and USI_OVERFLOW_vect).
// Set SCL and SDA as output
DDR_USI |= ( 1 << PORT_USI_SCL ) | ( 1 << PORT_USI_SDA );
// set SCL high
PORT_USI |= ( 1 << PORT_USI_SCL );
// set SDA high
PORT_USI |= ( 1 << PORT_USI_SDA );
// Set SDA as input
DDR_USI &= ~( 1 << PORT_USI_SDA );
USICR =
// enable Start Condition Interrupt
( 1 << USISIE ) |
// disable Overflow Interrupt
( 0 << USIOIE ) |
// set USI in Two-wire mode, no USI Counter overflow hold
( 1 << USIWM1 ) | ( 0 << USIWM0 ) |
// Shift Register Clock Source = external, positive edge
// 4-Bit Counter Source = external, both edges
( 1 << USICS1 ) | ( 0 << USICS0 ) | ( 0 << USICLK ) |
// no toggle clock-port pin
( 0 << USITC );
// clear all interrupt flags and reset overflow counter
USISR = ( 1 << USI_START_COND_INT ) | ( 1 << USIOIF ) | ( 1 << USIPF ) | ( 1 << USIDC );
} // end usiTwiSlaveInit
bool usiTwiDataInTransmitBuffer(void)
{
// return 0 (false) if the receive buffer is empty
return txHead != txTail;
} // end usiTwiDataInTransmitBuffer
// put data in the transmission buffer, wait if buffer is full
void
usiTwiTransmitByte(
uint8_t data
)
{
uint8_t tmphead;
// calculate buffer index
tmphead = ( txHead + 1 ) & TWI_TX_BUFFER_MASK;
// wait for free space in buffer
while ( tmphead == txTail );
// store data in buffer
txBuf[ tmphead ] = data;
// store new index
txHead = tmphead;
} // end usiTwiTransmitByte
// return a byte from the receive buffer, wait if buffer is empty
uint8_t
usiTwiReceiveByte(
void
)
{
// wait for Rx data
while ( rxHead == rxTail );
// calculate buffer index
rxTail = ( rxTail + 1 ) & TWI_RX_BUFFER_MASK;
// return data from the buffer.
return rxBuf[ rxTail ];
} // end usiTwiReceiveByte
// check if there is data in the receive buffer
bool
usiTwiDataInReceiveBuffer(
void
)
{
// return 0 (false) if the receive buffer is empty
return rxHead != rxTail;
} // end usiTwiDataInReceiveBuffer
/********************************************************************************
USI Start Condition ISR
********************************************************************************/
ISR( USI_START_VECTOR )
{
// set default starting conditions for new TWI package
overflowState = USI_SLAVE_CHECK_ADDRESS;
// set SDA as input
DDR_USI &= ~( 1 << PORT_USI_SDA );
// wait for SCL to go low to ensure the Start Condition has completed (the
// start detector will hold SCL low ) - if a Stop Condition arises then leave
// the interrupt to prevent waiting forever - don't use USISR to test for Stop
// Condition as in Application Note AVR312 because the Stop Condition Flag is
// going to be set from the last TWI sequence
while (
// SCL his high
( PIN_USI & ( 1 << PIN_USI_SCL ) ) &&
// and SDA is low
!( ( PIN_USI & ( 1 << PIN_USI_SDA ) ) )
);
if ( !( PIN_USI & ( 1 << PIN_USI_SDA ) ) )
{
// a Stop Condition did not occur
USICR =
// keep Start Condition Interrupt enabled to detect RESTART
( 1 << USISIE ) |
// enable Overflow Interrupt
( 1 << USIOIE ) |
// set USI in Two-wire mode, hold SCL low on USI Counter overflow
( 1 << USIWM1 ) | ( 1 << USIWM0 ) |
// Shift Register Clock Source = External, positive edge
// 4-Bit Counter Source = external, both edges
( 1 << USICS1 ) | ( 0 << USICS0 ) | ( 0 << USICLK ) |
// no toggle clock-port pin
( 0 << USITC );
}
else
{
// a Stop Condition did occur
USICR =
// enable Start Condition Interrupt
( 1 << USISIE ) |
// disable Overflow Interrupt
( 0 << USIOIE ) |
// set USI in Two-wire mode, no USI Counter overflow hold
( 1 << USIWM1 ) | ( 0 << USIWM0 ) |
// Shift Register Clock Source = external, positive edge
// 4-Bit Counter Source = external, both edges
( 1 << USICS1 ) | ( 0 << USICS0 ) | ( 0 << USICLK ) |
// no toggle clock-port pin
( 0 << USITC );
} // end if
USISR =
// clear interrupt flags - resetting the Start Condition Flag will
// release SCL
( 1 << USI_START_COND_INT ) | ( 1 << USIOIF ) |
( 1 << USIPF ) |( 1 << USIDC ) |
// set USI to sample 8 bits (count 16 external SCL pin toggles)
( 0x0 << USICNT0);
} // end ISR( USI_START_VECTOR )
/********************************************************************************
USI Overflow ISR
Handles all the communication.
Only disabled when waiting for a new Start Condition.
********************************************************************************/
ISR( USI_OVERFLOW_VECTOR )
{
switch ( overflowState )
{
// Address mode: check address and send ACK (and next USI_SLAVE_SEND_DATA) if OK,
// else reset USI
case USI_SLAVE_CHECK_ADDRESS:
if ( ( USIDR == 0 ) || ( ( USIDR >> 1 ) == slaveAddress) )
{
// callback
if(_onTwiDataRequest) _onTwiDataRequest();
if ( USIDR & 0x01 )
{
overflowState = USI_SLAVE_SEND_DATA;
}
else
{
overflowState = USI_SLAVE_REQUEST_DATA;
} // end if
SET_USI_TO_SEND_ACK( );
}
else
{
SET_USI_TO_TWI_START_CONDITION_MODE( );
}
break;
// Master write data mode: check reply and goto USI_SLAVE_SEND_DATA if OK,
// else reset USI
case USI_SLAVE_CHECK_REPLY_FROM_SEND_DATA:
if ( USIDR )
{
// if NACK, the master does not want more data
SET_USI_TO_TWI_START_CONDITION_MODE( );
return;
}
// from here we just drop straight into USI_SLAVE_SEND_DATA if the
// master sent an ACK
// copy data from buffer to USIDR and set USI to shift byte
// next USI_SLAVE_REQUEST_REPLY_FROM_SEND_DATA
case USI_SLAVE_SEND_DATA:
// Get data from Buffer
if ( txHead != txTail )
{
txTail = ( txTail + 1 ) & TWI_TX_BUFFER_MASK;
USIDR = txBuf[ txTail ];
}
else
{
// the buffer is empty
SET_USI_TO_TWI_START_CONDITION_MODE( );
return;
} // end if
overflowState = USI_SLAVE_REQUEST_REPLY_FROM_SEND_DATA;
SET_USI_TO_SEND_DATA( );
break;
// set USI to sample reply from master
// next USI_SLAVE_CHECK_REPLY_FROM_SEND_DATA
case USI_SLAVE_REQUEST_REPLY_FROM_SEND_DATA:
overflowState = USI_SLAVE_CHECK_REPLY_FROM_SEND_DATA;
SET_USI_TO_READ_ACK( );
break;
// Master read data mode: set USI to sample data from master, next
// USI_SLAVE_GET_DATA_AND_SEND_ACK
case USI_SLAVE_REQUEST_DATA:
overflowState = USI_SLAVE_GET_DATA_AND_SEND_ACK;
SET_USI_TO_READ_DATA( );
break;
// copy data from USIDR and send ACK
// next USI_SLAVE_REQUEST_DATA
case USI_SLAVE_GET_DATA_AND_SEND_ACK:
// put data into buffer
// Not necessary, but prevents warnings
rxHead = ( rxHead + 1 ) & TWI_RX_BUFFER_MASK;
rxBuf[ rxHead ] = USIDR;
// next USI_SLAVE_REQUEST_DATA
overflowState = USI_SLAVE_REQUEST_DATA;
SET_USI_TO_SEND_ACK( );
break;
} // end switch
} // end ISR( USI_OVERFLOW_VECTOR )
#endif /* TEST */
Raw
usiTwiSlave.h
/********************************************************************************
Header file for the USI TWI Slave driver.
Created by Donald R. Blake
donblake at worldnet.att.net
---------------------------------------------------------------------------------
Created from Atmel source files for Application Note AVR312: Using the USI Module
as an I2C slave.
This program is free software; you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE. See the GNU General Public License for more details.
---------------------------------------------------------------------------------
Change Activity:
Date Description
------ -------------
15 Mar 2007 Created.
********************************************************************************/
#ifndef _USI_TWI_SLAVE_H_
#define _USI_TWI_SLAVE_H_
/********************************************************************************
includes
********************************************************************************/
#include <stdbool.h>
/********************************************************************************
prototypes
********************************************************************************/
void usiTwiSlaveInit( uint8_t );
void usiTwiTransmitByte( uint8_t );
uint8_t usiTwiReceiveByte( void );
bool usiTwiDataInReceiveBuffer( void );
void (*_onTwiDataRequest)(void);
bool usiTwiDataInTransmitBuffer(void);
/********************************************************************************
driver buffer definitions
********************************************************************************/
// permitted RX buffer sizes: 1, 2, 4, 8, 16, 32, 64, 128 or 256
#define TWI_RX_BUFFER_SIZE ( 16 )
#define TWI_RX_BUFFER_MASK ( TWI_RX_BUFFER_SIZE - 1 )
#if ( TWI_RX_BUFFER_SIZE & TWI_RX_BUFFER_MASK )
# error TWI RX buffer size is not a power of 2
#endif
// permitted TX buffer sizes: 1, 2, 4, 8, 16, 32, 64, 128 or 256
#define TWI_TX_BUFFER_SIZE ( 16 )
#define TWI_TX_BUFFER_MASK ( TWI_TX_BUFFER_SIZE - 1 )
#if ( TWI_TX_BUFFER_SIZE & TWI_TX_BUFFER_MASK )
# error TWI TX buffer size is not a power of 2
#endif
#endif // ifndef _USI_TWI_SLAVE_H_
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